In a communication system, the role of a control unit is, among other things to control the resource allocation at access points connected to the control unit. In order to be able to perform this task, the control unit requests, from the access points, measurement reports containing measurements regarding links associated with the access points, measurements which are necessary for e.g. being able to control the resource allocation at the access points. The measurement reports are evaluated in the control unit, and based on the evaluation, commands are sent from the control unit to the access points.
As an example of such a communication system, FIG. 1 shows an exemplary mobile communication system 100. It comprises mobile terminals 101 in contact with access points 103 via links 102 over an access interface, which for the exemplary mobile communication system is an air interface. For the mobile communication network, the geographical position of the terminal defines to which access point the terminal is presently in contact. Each terminal 101 is in contact with its access point 103 via at least one link 102. The access points are in their turn connected via control interfaces 104 to a control unit 105. The control interface 104 is defined as a connection between one control unit 105 and one access point 103. In FIG. 1, for clarity reasons, only one control unit 105, one access point 103 and consequently only one control interface 104 is shown, although, it would be apparent to a person skilled in the art that a communication system may comprise many control units, access points and control interfaces.
As mentioned above, the control unit 105 controls the resource allocation at the access point 103 connected to the control unit. This control is managed by algorithms in subunits 205, 206 in the control unit 105. For this purpose, the control unit requests measurement information from the access point 103 regarding the links 102 associated with the access point 103. The measurements could be of different types depending on what is requested by the algorithms. In the example of a mobile communication system, the measurement types could be e.g.: received interference level, transmitted power level, path-loss, received signal quality, etc.
A common practice is that each subunit 205, 206 in the control unit 105 requests its own measurements necessary for its algorithm from the access point 103 on a per link basis. The measurement requests, sent by the control unit 105, specify the type of measurements to send and with which frequency they should be sent. In response, the access point 103 compiles so called periodic measurement reports, which are sent to the subunits 205, 206 in the control unit 105 at the requested frequency comprising the requested measurements. Different types of periodic measurement reports could be sent at different frequencies depending on what is being reported.
The measurement reports are necessary for the system to know e.g. the quality of a link 102 and to be able to take necessary steps if for example the quality of a link deteriorates. Such steps could e.g. be that the mobile communication network performs handover of a terminal 101 to another access point 103. Therefore, the more often measurement reports are received at the control unit 105 for evaluation, the better the control of the communication over each link 102. On the other hand, there are capacity limitations over the control interface 104 and in the processors in the access point 103 that limits the amount of measurement reports that could be sent to the control unit 105 over the control interface 104.
As the different subunits 205, 206 in the control unit requests their own measurement reports from the access point 103 and as the algorithms in the subunits may request reports comprising different measurement types for one link, an access point may have to send more than one periodic measurement report per link. Therefore, and especially since an access point 103 may accommodate e.g. 100 links, the total number of different possible periodic measurement reports may become quite large over one control interface 104. Since at the same time, as described above, there are capacity limitations regarding the amount of measurement reports possible to send to the control unit 105 over the control interface 104, there is a need to control the reporting frequency of the periodic measurement reports sent over the control interface.
The international patent application WO 00/76233 shows a prior art system for controlling the communication of measurement reports in a mobile communication system. It deals with limiting the number of measurement reports sent from a terminal 101 over a link 102 in the access interface to the access point 103 that the terminal 101 is connected to.
The international patent application WO 02/73887 shows another prior art system for controlling the communication of measurement reports within a mobile communication system. This document deals with the problem of having limited resources in the processor in the access point 103. The load of the processor is controlled by controlling the reporting of measurements within the access point 103.
None of the prior art documents discuss controlling the communication of measurement reports from an access point to a control unit considering the request sent by the control unit.
As could be seen above, there is a need for a system for efficiently controlling the communication of measurement reports from an access point 103 over a control interface 104 to a control unit 105.